Isotretinoin Cumulative Dose Calculator
Dermatologists aim for a cumulative isotretinoin dose of 120–150 mg/kg over the full treatment course to minimise relapse risk. Enter your weight, daily dose and planned treatment duration to see your projected cumulative dose and how it compares to that target.
kg
Weight unit
mg/kg/day
weeks
Total dose per kg body weight — target is 120–150 mg/kg for a full course
- 1
Daily dose (mg)
1 × 70 = 70 mgDose rate (mg/kg/day) multiplied by body weight gives the actual daily milligrams. - 2
Treatment days
20 × 7 = 140 days - 3
Total cumulative dose
70 × 140 = 9,800 mg - 4
Cumulative dose per kg
9,800 ÷ 70 = 140
How does this calculator work?
Cumulative dose (mg/kg) = daily dose (mg/kg/day) × weight (kg) × days ÷ weight. The clinical target is 120–150 mg/kg over the full course, typically achieved in 16–24 weeks at 0.5–1 mg/kg/day. A 70 kg patient on 1 mg/kg/day hits 140 mg/kg after 20 weeks.
Formula
How this is calculated
Isotretinoin (Accutane/Roaccutane) is dosed by body weight. A physician typically prescribes 0.5–1 mg/kg/day, meaning a 70 kg patient on 1 mg/kg/day takes 70 mg per day. Over a 20-week course (140 days) that totals 9,800 mg, or 140 mg/kg — squarely in the evidence-backed target window of 120–150 mg/kg associated with the lowest relapse rates.
This calculator multiplies your daily dose rate by your weight to get the daily dose in milligrams, then multiplies by the number of treatment days (weeks × 7) to get the total cumulative dose. Dividing by weight converts this back to mg/kg for comparison with the clinical target. If you enter pounds, weight is converted to kilograms using 1 lb = 0.4536 kg.
The target range and dosing guidelines reflect standard clinical practice as of 2024; your dermatologist may choose a different protocol based on your specific skin type, side-effect profile and prior response. This tool is for educational awareness only — never adjust your prescribed dose without medical advice.
Frequently asked questions
Clinical trials and long-term follow-up studies have consistently shown that patients who complete a cumulative dose in this range have lower relapse rates than those who stop earlier. Going significantly above 150 mg/kg does not improve outcomes but increases side-effect risk.
You may need a longer course or a higher daily dose, subject to your dermatologist's judgment. Some patients with mild acne or high sensitivity are managed on lower cumulative doses intentionally.
No. Isotretinoin is a teratogen and a tightly regulated prescription medicine in most countries (e.g. iPLEDGE in the US). It requires physician oversight, regular blood tests, and mandatory contraception for women of childbearing potential.
Also known as
TG we-Calculate Editorial Team. (2026). Isotretinoin Cumulative Dose Calculator [Online calculator]. TG we-Calculate. https://we-calculate.com/calculator/isotretinoin-calculator
TG we-Calculate Editorial Team. "Isotretinoin Cumulative Dose Calculator." TG we-Calculate. 2026. https://we-calculate.com/calculator/isotretinoin-calculator.
TG we-Calculate Editorial Team, "Isotretinoin Cumulative Dose Calculator," TG we-Calculate, 2026. [Online]. Available: https://we-calculate.com/calculator/isotretinoin-calculator
@misc{wecalculate_isotretinoin_calculator, title = {Isotretinoin Cumulative Dose Calculator}, author = {{TG we-Calculate Editorial Team}}, howpublished = {\url{https://we-calculate.com/calculator/isotretinoin-calculator}}, year = {2026}, note = {TG we-Calculate} }
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